(a) Field of the Invention
The present invention relates to novel trisazo compounds, a process for the preparation of said trisazo compounds, and electrophotographic sensitive materials comprising said compounds or analogues thereof as effective ingredient.
(b) Description of the Prior Art
It is known that some organic compounds, e.g., indigotype compounds, phthalocyanine compounds, etc., are useful as a photoconductive material to be employed for the electrophotographic process. The "electrophotographic process" herein is one of the image-forming processes which generally comprises first charging a photoconductive sensitive material with electricity by corona discharge or the like in the dark, subsequently subjecting it to image-wise exposure so as to discharge the electric charge of the exposed area selectively, thereby obtaining an electrostatic latent image, and then rendering visible this latent image by a developing means employing a toner or the like, thereby forming an intended image. As the fundamental characteristics required for the photosensitive materials for use in the electrophotographic process, there are enumerated (1) chargeability in the dark to attain an appropriate potential, (2) low dischargeability in the dark, and (3) rapid dischargeability upon exposure to light. As a matter of fact, however, the hitherto known organic photoconductive compounds have not always sufficiently satisfied these requirements.
Some inorganic simple substances or inorganic compounds such as selenium, zinc oxide, etc. are also known as useful photoconductive materials, of which selenium has admittedly been widely put to practical use. However, with the adoption of various processes in the latest electrophotographic process art, there is an increasing demand for a photosensitive material suitable for any of these processes, that is, a demand for, for instance, a belt-shaped photosensitive material having flexibility with respect to its shape in addition to the aforementioned fundamental characteristics. In this regard, selenium is generally difficult to form into a photosensitive material having such a shape as discussed above.
Meanwhile, there are known electrophotographic sensitive materials prepared by forming a photosensitive layer containing some azo compound, as an effective ingredient, on a conductive support such as, for instance, one prepared by employing monoazo compound as disclosed in Japanese Patent Publication No. 16474/1969 and one prepared by employing disazo compound as disclosed in U.S. Pat. Nos. 3,898,048 and 4,052,210. These azo compounds are admittedly useful materials as an effective ingredient of photosensitive materials, but when various requirements for photosensitive materials are taken into account from the viewpoint of the electrophotographic process, there has in fact not yet been obtained such a material as will sufficiently meet these requirements. Therefore, it is a matter of more importance to provide a wide variety of compounds, not limiting to azo compounds, so as to afford a wide range of selection of compounds acting as an effective ingredient according to various electrophotographic processes, thereby rendering it possible to provide a photosensitive material apposite to any specific process. In other words, it is desirable for the electrophotographic process that the variety of compounds workable as an effective ingredient of photosensitive materials is as wide as possible.